... or do it till it's done ;)
Alrighty righty ! This is the second part of my six C64s restoration/upgrade project. The first part for all of you who didn't see it is here
More on keyboards
At the beginning, I didn't plan to write about keyboard caps whitening but I had to do it anyway, so why not showing how it looked :)
I had five remaining keyboards to clean and whiten a bit so I decided to go an easy way this time.
Obviously, I had to unscrew tiny PCB screws. A quick cleaning with IPA helped to remove dust and other gunk.
Nothing really complicated, however, there was one curio. On one of the PCBs, I've found crappy solder joints. It wouldn't be a surprise on a high-voltage circuit but here ? Looks like a factory-made error, so I've basically scraped it off and cleaned with IPA.
That's all about KB PCBs. Let's move on to whitening.
Here is a photo before I started.
Two of the keyboards are yellow like nutrias teeth and one (bottom one) is simply dirty. A detailed method of whitening was described in my previous post, however, there are three hints worth mentioning.
First is to simply leave key caps on a plastic frame and use a brush to apply whitening cream instead of doing every single key cap separately. That saves a lot of time. Here is a photo.
The second hint was posted in a comment section of my previous post about C64 refurbishing. Elwood89 (thanks, buddy!) suggested using stretch-wrap to eliminate excessive moist evaporation. I will have to try that approach someday.
And finally, the third hint is my new discovery.
I was doing keyboards whitening on Friday afternoon. Obviously, every Friday evening there is a lot happening .....
... most probably (I cannot confirm that for sure :D) that was a direct cause of completely forgetting about keyboards.
Next morning (well, it wasn't morning exactly), I rushed (well, maybe not rushed) to see if my keyboards are totally messed up.
To my surprise, all was OK and even evenly whitened !
The only explanation that comes to my head is that morning dew sorted out a moisture evaporation problem for me. Also, the sun isn't that strong in a morning so it all had a nice stable sun bath for quite a while. I'll recheck that hypothesis again one day .... most probably Friday :>
Anyway, bottom line is - DRINKING FRIDAYS FTW !!!
Fortunately, that was an easy fix. I only needed a bit of acetone and a small brush to apply it to broken surfaces. A while of holding broken pieces together in place, resulted in getting a nearly invisible scratch.
PCB cleaning and minor repairs
All PCBs were in a decent state but required a bit of cleaning. There were only two electrical problems that I noticed, bet let's start with cleaning first.
All PCBs were covered in old dust that had to be removed. I usually use an air compressor to remove it and after that, IPA with a paint brush takes care of the rest.
I also use IPA with a toothbrush to all other gunk. In most cases it cleans up easily.
From the electrical point of view, it is not a problem since this area connects ground planes on both sides of PCB and there are still a lot of additional vias nearby that serve the same purpose. However, if that corrosion spreads further, it might start to be a problem. That's why I scraped it off, sanded with grit 400 sand paper and covered it with rosin dissolved in IPA.
The second problem was with Character ROM. I've seen this kind of errors in past so I instantly knew that it is caused either by faulty IC (not likely in my case) or broken traces/contacts. A closer look revealed that someone desoldered this chip in past. I did my best to desolder it carefully, however, it still looked quite hopeless.
To fix missing VIAs I've simply scraped off a bit of solder mask and soldered a piece of wire through damaged VIA. Unfortunately, I forgot to take a photo of this repair.
Broken trace was fixed in a similar way but this time, I've soldered it to a remaining trace and directly to IC pin. Maybe not best-looking repair but it proved to work like a charm. :>
JiffyDOS is an awesome piece of software that is programmed directly onto ROM chips that replace the Kernal ROM chip. That is why I needed to install sockets in a first place.
I wanted to do some minor changes to ROM images prior to burning it to flash ROM <-- I dunno if it is legal, though.
Aaaaha ! a flash ROM ? dafaq ? how ? ... yeah a flash ROM , SST27SF512 for example.
SST27SFxxx series is a nearly perfect replacement for original 251913-01 chip. Using flash ROM is very convenient. You can simply flash it and in the case of an error easily repeat a process without using UV lamp to reset a chip.
Here is an original IC
All six motherboards that I have are pretty much identical. All of them has a 251913-01 chip which stores 8kB basic + 8kB kernal, so there are 16kB of data that has to be written on a destination flash ROM. JiffyDOS comes as an 8kB bin image so that part is sorted. However, 8kB of basic is also needed to get a complete 16kB bin image.
There are at least two ways to solve it. You can either dump 16kB of data from original 251913-01 and cut it in half (with a dd cmd under Linux for example) so you will get an 8kB basic bin or you can browse the web for already dumped 8kB basic.
Then you can simply merge these two (8kB basic + 8kB JiffyDOS) images into one 16kB bin and flash it to IC.
Prior to flashing a 27SF512 I did few changes with a bin image in hex editor and tested it under Vice which resulted in this :)
Also, keep in mind that for this to work, 16kB of data has to be flashed onto SST27SF512 with a C0000 offset. More info here
To programm a flash ROM I usually use my crappy Willem EZO.
That was actually the main reason for buying all four C64s, I mean missing SIDs.
I've built several SwinSIDs in past so It was just a matter of inserting it and testing - no flying hogs involved :D
Still not the end ...
... of a project. In part three I'll cover SD2IEC installation, paint job and final assembly of all C64s. Till then, just have a look at already finished C64 Version G :)